In crown and bridge prosthodontics, dental copings of metal are conventionally used to provide the essential structural strength and rigidity necessary for a dental restoration to resist the forces of mastication when food is eaten. In a ceramic-to-metal dental restoration, the metal coping forms the understructure of a dental crown and/or a bridge, over which is applied a fired-on coating of porcelain or a polymer based veneering material.
A metal coping may be cast from an investment of a wax or plastic pattern of the tooth to be restored. An alternative procedure for forming a precious metal coping which does not require waxing, investing or casting has currently been gaining wide acceptance in the dental profession by both dentists and dental laboratories. This alternative procedure requires the use of a moldable material composition formed from a base material composition of high and low fusing temperature metal particles and a binder preferably of dental wax as is disclosed, for example, in U.S. Pat. Nos. 5,234,343, 5,593,305 and 5,730,600 respectively, each disclosure of which is herein incorporated by reference.
In accordance with the teaching of the aforementioned patents the moldable material is hand molded over a die which has the shape of the tooth to be restored. The heat treating temperature must be above the melting temperature of the low fusing temperature metal particles of the moldable material and below the melting temperature of the high fusing temperature metal particles. Heat treatment transforms the hand molded structure into a porous metallic shell having the same shape as before heat treatment without suffering any significant shrinkage. The wax in the molded material vaporizes during heat treatment leaving the porous metallic shell with a high void volume of preferably above at least 20%. A filler material of metal or ceramic is melted into the porous shell to densify and solidify the shell into the dental coping over which may be applied a fired-on coating of porcelain or a polymer based veneering material for aesthetics. The filler material is preferably of a precious metal such as gold or a gold alloy in a wax binder.
The geometry of the base and filler materials are currently made available to the dental laboratory in the form of thin compacted strips of rectangular geometry. The hand molding operation is a procedure in which the conventional strip of base material is cut into separate pieces each of which is separately applied to the die by hand followed by hand pressing the pieces against the die. A hand burnishing tool may be used to assist the technician. This procedure of hand pressing the material to hand mold it to the surface of the die is time consuming and labor intensive. During the formation of the coping the filler material may be added to the molded structure either in a secondary heat treatment operation or during the primary heat treatment of the coping shell.
The objective of the present invention is to provide an adaptation device and method to assist the laboratory technician or dentist in molding dental material to the die before heat treatment so as to minimize the labor intensive characteristic of the procedure and to substantially increase the speed of forming a mold while assuring uniformity in the quality of the molded structure.